Self-aspirating/air-preheating porous medium gas burner

• Published in: Applied thermal engineering 2019-05, Vol.153, p.181-189
• Main Authors: Chaelek, Aekkaphon, Grare, Usa Makmool, Jugjai, Sumrerng
• Format: Article
• Language: English
• Subjects: Air preheating; Air temperature; Aluminum oxide; Atmospheric burner; Atmospheric circulation; Combustion chambers; Empirical equations; Equivalence ratio; Flame propagation; Flame temperature; Flow velocity; Heat conductivity; Heat recirculation combustion; Heating; Low NOx burner; Nitrogen oxides; Packed beds; Porous materials; Porous media; Porous medium burner; Pressure drop; Propagation velocity; Self-aspirating burner
• ISSN: 1359-4311; 1873-5606
• DOI: 10.1016/j.applthermaleng.2019.02.109

•An atmospheric gas porous medium burner with air preheating was developed.•Stable combustion was ensured for wide range of firing rate and equivalence ratio.•Operation of the burner from 21–44 kW resulted in air temperatures of 136–252 °C.•The combustion temperature reached is higher than adiabatic flame temperature.•An energy consumption reduced by 28.7% compared with the conventional burner. This study proposes a novel design of an atmospheric gas burner that introduces the concept of heat recirculation combustion by means of porous media combustion technology. A combustor and heat recirculation unit, used for preheating the combustion air, are part of the assembly of the porous material. The combustor is a self-aspirating annular porous medium burner (APMB) formed by a packed bed of alumina spheres with a diameter of 10 mm. A porous radiant recirculation heater was integrated into the APMB to obtain an elevated air temperature. To stabilize flames at the middle of the porous media packed bed, the flow velocity of the mixture has to be equal to the flame propagation velocity, making this a critical criterion for the design of the burner. A critical variable required to determine the flame velocity is the primary equivalence ratio. It was predicted using the empirical formula derived from the experimental data, and considers the momentum equation and pressure drop in the porous medium burner. Operation of the burner with firing rates from 21 to 44 kW resulted in evaluated air temperatures of 136–252 °C, yielding maximal temperatures greater than the adiabatic flame temperature. The NOx emissions were low because of the combustion within a porous medium. The CO emissions were high compared with the conventional burner but still conformed to the requirements of the national standard.